Stephen King, the guy who started planning at JWT, believed that all good advertising left gaps that people could fill in for themselves. He believed that when people did not have to work a little to understand communications, they would never care about or remember it:
"We often hear and understand what is said to us and can remember it later, but take no notice of it. It is only when we ACTIVELY consider what is said and adopt it as our own view that we have really responded.
"This means that the most successful communication is one that leaves room for active participation by the receiver; it works as much by what it leaves out as what it puts in. Jokes, for example, work by being implicit rather than explicit. Our comedian, if he had succeeded by telling a joke, could then have destroyed it by explaining it."
He goes to write,
"what advertising has to do is entice people into sharing a point of view and contributing their own interpretation - not bully them into acquiescence. Buyers are free agents, not recruits in a platoon of marines."